Have you heard of Aequorin from the jelly fish *Aequorin victoria*? In the
presence of Ca2+ it emits light of 469 nm wavelength (as opposed to
luciferin which emits light of 560 nm). The sensitivity of the reporter
gene assay, however is only as sensitive as CAT.
There is a good review article on reporter gene systems published last
year in Analytical Biochemistry 219, 169. It lists both bioluminescent
and chemiluminescent systems and has an interesting section on multiplexing.
If you can't get hold of it, I can send you a copy.